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diff --git a/docs/examples/crawler.c b/docs/examples/crawler.c
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+/***************************************************************************
+ * _ _ ____ _
+ * Project ___| | | | _ \| |
+ * / __| | | | |_) | |
+ * | (__| |_| | _ <| |___
+ * \___|\___/|_| \_\_____|
+ *
+ * Web crawler based on curl and libxml2.
+ * Copyright (C) 2018 Jeroen Ooms <jeroenooms@gmail.com>
+ * License: MIT
+ *
+ * To compile:
+ * gcc crawler.c $(pkg-config --cflags --libs libxml-2.0 libcurl)
+ *
+ */
+/* <DESC>
+ * Web crawler based on curl and libxml2 to stress-test curl with
+ * hundreds of concurrent connections to various servers.
+ * </DESC>
+ */
+
+/* Parameters */
+int max_con = 200;
+int max_total = 20000;
+int max_requests = 500;
+int max_link_per_page = 5;
+int follow_relative_links = 0;
+char *start_page = "https://www.reuters.com";
+
+#include <libxml/HTMLparser.h>
+#include <libxml/xpath.h>
+#include <libxml/uri.h>
+#include <curl/curl.h>
+#include <stdlib.h>
+#include <string.h>
+#include <math.h>
+#include <signal.h>
+
+int pending_interrupt = 0;
+void sighandler(int dummy)
+{
+ pending_interrupt = 1;
+}
+
+/* resizable buffer */
+typedef struct {
+ char *buf;
+ size_t size;
+} memory;
+
+size_t grow_buffer(void *contents, size_t sz, size_t nmemb, void *ctx)
+{
+ size_t realsize = sz * nmemb;
+ memory *mem = (memory*) ctx;
+ mem->buf = realloc(mem->buf, mem->size + realsize);
+ memcpy(&(mem->buf[mem->size]), contents, realsize);
+ mem->size += realsize;
+ return realsize;
+}
+
+CURL *make_handle(char *url)
+{
+ CURL *handle = curl_easy_init();
+
+ /* Important: use HTTP2 over HTTPS */
+ curl_easy_setopt(handle, CURLOPT_HTTP_VERSION, CURL_HTTP_VERSION_2TLS);
+ curl_easy_setopt(handle, CURLOPT_URL, url);
+
+ /* buffer body */
+ memory *mem = malloc(sizeof(memory));
+ mem->size = 0;
+ mem->buf = malloc(1);
+ curl_easy_setopt(handle, CURLOPT_WRITEFUNCTION, grow_buffer);
+ curl_easy_setopt(handle, CURLOPT_WRITEDATA, mem);
+ curl_easy_setopt(handle, CURLOPT_PRIVATE, mem);
+
+ /* For completeness */
+ curl_easy_setopt(handle, CURLOPT_ENCODING, "gzip, deflate");
+ curl_easy_setopt(handle, CURLOPT_TIMEOUT, 5L);
+ curl_easy_setopt(handle, CURLOPT_FOLLOWLOCATION, 1L);
+ curl_easy_setopt(handle, CURLOPT_MAXREDIRS, 10L);
+ curl_easy_setopt(handle, CURLOPT_CONNECTTIMEOUT, 2L);
+ curl_easy_setopt(handle, CURLOPT_COOKIEFILE, "");
+ curl_easy_setopt(handle, CURLOPT_FILETIME, 1L);
+ curl_easy_setopt(handle, CURLOPT_USERAGENT, "mini crawler");
+ curl_easy_setopt(handle, CURLOPT_HTTPAUTH, CURLAUTH_ANY);
+ curl_easy_setopt(handle, CURLOPT_UNRESTRICTED_AUTH, 1L);
+ curl_easy_setopt(handle, CURLOPT_PROXYAUTH, CURLAUTH_ANY);
+ curl_easy_setopt(handle, CURLOPT_EXPECT_100_TIMEOUT_MS, 0L);
+ return handle;
+}
+
+/* HREF finder implemented in libxml2 but could be any HTML parser */
+size_t follow_links(CURLM *multi_handle, memory *mem, char *url)
+{
+ int opts = HTML_PARSE_NOBLANKS | HTML_PARSE_NOERROR | \
+ HTML_PARSE_NOWARNING | HTML_PARSE_NONET;
+ htmlDocPtr doc = htmlReadMemory(mem->buf, mem->size, url, NULL, opts);
+ if(!doc)
+ return 0;
+ xmlChar *xpath = (xmlChar*) "//a/@href";
+ xmlXPathContextPtr context = xmlXPathNewContext(doc);
+ xmlXPathObjectPtr result = xmlXPathEvalExpression(xpath, context);
+ xmlXPathFreeContext(context);
+ if(!result)
+ return 0;
+ xmlNodeSetPtr nodeset = result->nodesetval;
+ if(xmlXPathNodeSetIsEmpty(nodeset)) {
+ xmlXPathFreeObject(result);
+ return 0;
+ }
+ size_t count = 0;
+ for(int i = 0; i < nodeset->nodeNr; i++) {
+ double r = rand();
+ int x = r * nodeset->nodeNr / RAND_MAX;
+ const xmlNode *node = nodeset->nodeTab[x]->xmlChildrenNode;
+ xmlChar *href = xmlNodeListGetString(doc, node, 1);
+ if(follow_relative_links) {
+ xmlChar *orig = href;
+ href = xmlBuildURI(href, (xmlChar *) url);
+ xmlFree(orig);
+ }
+ char *link = (char *) href;
+ if(!link || strlen(link) < 20)
+ continue;
+ if(!strncmp(link, "http://", 7) || !strncmp(link, "https://", 8)) {
+ curl_multi_add_handle(multi_handle, make_handle(link));
+ if(count++ == max_link_per_page)
+ break;
+ }
+ xmlFree(link);
+ }
+ xmlXPathFreeObject(result);
+ return count;
+}
+
+int is_html(char *ctype)
+{
+ return ctype != NULL && strlen(ctype) > 10 && strstr(ctype, "text/html");
+}
+
+int main(void)
+{
+ signal(SIGINT, sighandler);
+ LIBXML_TEST_VERSION;
+ curl_global_init(CURL_GLOBAL_DEFAULT);
+ CURLM *multi_handle = curl_multi_init();
+ curl_multi_setopt(multi_handle, CURLMOPT_MAX_TOTAL_CONNECTIONS, max_con);
+ curl_multi_setopt(multi_handle, CURLMOPT_MAX_HOST_CONNECTIONS, 6L);
+
+ /* enables http/2 if available */
+ #ifdef CURLPIPE_MULTIPLEX
+ curl_multi_setopt(multi_handle, CURLMOPT_PIPELINING, CURLPIPE_MULTIPLEX);
+ #endif
+
+ /* sets html start page */
+ curl_multi_add_handle(multi_handle, make_handle(start_page));
+
+ int msgs_left;
+ int pending = 0;
+ int complete = 0;
+ int still_running = 1;
+ while(still_running && !pending_interrupt) {
+ int numfds;
+ curl_multi_wait(multi_handle, NULL, 0, 1000, &numfds);
+ curl_multi_perform(multi_handle, &still_running);
+
+ /* See how the transfers went */
+ CURLMsg *m = NULL;
+ while((m = curl_multi_info_read(multi_handle, &msgs_left))) {
+ if(m->msg == CURLMSG_DONE) {
+ CURL *handle = m->easy_handle;
+ char *url;
+ memory *mem;
+ curl_easy_getinfo(handle, CURLINFO_PRIVATE, &mem);
+ curl_easy_getinfo(handle, CURLINFO_EFFECTIVE_URL, &url);
+ if(m->data.result == CURLE_OK) {
+ long res_status;
+ curl_easy_getinfo(handle, CURLINFO_RESPONSE_CODE, &res_status);
+ if(res_status == 200) {
+ char *ctype;
+ curl_easy_getinfo(handle, CURLINFO_CONTENT_TYPE, &ctype);
+ printf("[%d] HTTP 200 (%s): %s\n", complete, ctype, url);
+ if(is_html(ctype) && mem->size > 100) {
+ if(pending < max_requests && (complete + pending) < max_total) {
+ pending += follow_links(multi_handle, mem, url);
+ still_running = 1;
+ }
+ }
+ }
+ else {
+ printf("[%d] HTTP %d: %s\n", complete, (int) res_status, url);
+ }
+ }
+ else {
+ printf("[%d] Connection failure: %s\n", complete, url);
+ }
+ curl_multi_remove_handle(multi_handle, handle);
+ curl_easy_cleanup(handle);
+ free(mem->buf);
+ free(mem);
+ complete++;
+ pending--;
+ }
+ }
+ }
+ curl_multi_cleanup(multi_handle);
+ curl_global_cleanup();
+ return 0;
+}